fix(ios): content-true viewport anchoring while scrollback evicts at the cap - #11185
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Included review availability: Your plan provides up to 10 included reviews per hour; 7 remain after this review. 📝 WalkthroughWalkthroughThe change tracks cumulative local scrollback pushes during output processing. Verified replay anchors and held pixel-scroll positions use this count to preserve content-relative positions across scrollback growth, eviction, and row-space changes. ChangesScrollback Position Preservation
Estimated code review effort: 3 (Moderate) | ~25 minutes Merge Risk: 🔵 Low · up to The PR keeps scrolled-up content stable during capped scrollback eviction, but row-space changes caused by reflow or erase may still place a held gesture or restored viewport at the wrong content position. This is a bounded iOS scrolling correctness risk requiring owner awareness before merge. Sequence Diagram(s)sequenceDiagram
participant RenderGrid
participant GhosttySurfaceView
participant VerifiedReplayViewportAnchor
RenderGrid->>GhosttySurfaceView: provide scrolledRows
GhosttySurfaceView->>GhosttySurfaceView: update localScrollbackRowsPushed
GhosttySurfaceView->>VerifiedReplayViewportAnchor: capture rowsPushedAtCapture
GhosttySurfaceView->>VerifiedReplayViewportAnchor: restore with rowsPushedSinceCapture
VerifiedReplayViewportAnchor-->>GhosttySurfaceView: return push-aware targetTopRow
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Full details: Cmux Swift Actor IsolationExplanation PASS. The production diff adds no actor-isolation failure covered by the rule. The new shared mutable counter uses Full details: Cmux Swift Blocking RuntimeExplanation The PR adds a production manual lock: Resolution Remove the new Full details: Cmux Browser Automation Off-MainExplanation PASS: The patch changes only eight iOS terminal/shell files and tests. It does not change Full details: Cmux Expensive Synchronous LoadExplanation PASS: The PR does not add or move an expensive agent-history load. The production diff only adds scrollback-counter accounting and terminal scroll/replay logic. Searches of all changed production Swift files found no Full details: Cmux Cache Substitution CorrectnessExplanation PASS — the production diff does not replace a fresh authoritative read with a cache in a persistence, history, undo, or snapshot path. Full details: Cmux No Hacky SleepsExplanation PASS: The full PR range from origin/main to HEAD changes only Full details: Cmux Algorithmic ComplexityExplanation PASS. The PR adds only constant-time arithmetic and lock reads for the push counter and anchor rebasing. The pixel-scroll retry remains a fixed Full details: Cmux Swift ConcurrencyExplanation PASS. The PR diff adds no new Full details: Cmux Swift `@Concurrent`Explanation PASS: The full pull request adds no Full details: Cmux Swift Package BoundariesExplanation PASS. The production diff stays behind existing SwiftPM boundaries: the terminal logic is in Full details: Cmux Swiftpm LockfilesExplanation PASS: The PR changes only iOS Swift source and test files. It does not change any Package.swift, Package.resolved, .gitignore, workflow, or Xcode project/package-reference file. The package and root Xcode lockfiles are unchanged, and tracked cmux package .gitignore files do not ignore Package.resolved. The SwiftPM lockfile policy is therefore not violated. Full details: Cmux Swift LoggingExplanation PASS. The PR adds no Full details: Cmux User-Facing Error PrivacyExplanation PASS. The PR changes scrollback and viewport state handling. It does not add or modify user-facing errors, alerts, command output, API error bodies, or recovery copy. The only added text is source documentation/comments and a Full details: Cmux Full InternationalizationExplanation PASS. The PR changes only iOS terminal scroll-state and viewport-anchor logic, plus tests. Added production text is limited to comments and a Full details: Cmux Swiftui State LayoutExplanation PASS. The complete PR diff adds no Full details: Cmux Architecture RethinkExplanation The PR introduces a lock-protected cross-generation side channel instead of keeping row-space state with its owner. Resolution Move the cumulative push counter into the generation-owned Full details: Cmux Swift Auxiliary Window Close ShortcutsExplanation PASS. The PR changes terminal scrollback accounting, replay viewport anchors, and pixel-scroll state. The full diff from origin/main adds or changes no NSWindow, NSPanel, NSWindowController, SwiftUI Window, WindowGroup, close-shortcut routing, or auxiliary-window identifier code. The deterministic checker also passes: scripts/lint_auxiliary_window_close_shortcuts.py reports all 36 identifiers valid. Full details: Cmux Source ArtifactsExplanation All 10 changed paths are Swift source or test files under the expected Packages/iOS Sources and Tests locations. The diff adds no artifact-like paths, binary files, logs, screenshots, recordings, caches, temporary directories, build output, or package-manager downloads. The new files have normal source/test modes, and Full details: Cmux No Test Or Debug Seam In Production SourceExplanation The PR worsens a test/debug seam in Resolution Remove the Full details: Cmux No Ambient Global StateExplanation No ambient global state was introduced. The new mutable counter is an instance property of Full details: Description checkExplanation The description provides a detailed summary, rationale, implementation scope, residual risk, and test results. However, it omits the required Demo Video, Review Trigger, and Checklist sections from the repository template.
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In
`@Packages/iOS/CmuxMobileTerminal/Sources/CmuxMobileTerminal/GhosttySurfaceView.swift`:
- Around line 345-346: Document at localScrollbackRowsPushed why
OSAllocatedUnfairLock is required, explicitly noting why actor or MainActor
ownership cannot preserve the required outputQueue ordering; alternatively, move
this shared state so outputQueue is its sole owner.
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Packages/iOS/CmuxMobileShellUI/Sources/CmuxMobileShellUI/GhosttySurfaceRepresentable.swiftPackages/iOS/CmuxMobileTerminal/Sources/CmuxMobileTerminal/GhosttySurfaceView+LocalPixelScroll.swiftPackages/iOS/CmuxMobileTerminal/Sources/CmuxMobileTerminal/GhosttySurfaceView+ThemeOutput.swiftPackages/iOS/CmuxMobileTerminal/Sources/CmuxMobileTerminal/GhosttySurfaceView+VerifiedReplay.swiftPackages/iOS/CmuxMobileTerminal/Sources/CmuxMobileTerminal/GhosttySurfaceView.swiftPackages/iOS/CmuxMobileTerminal/Sources/CmuxMobileTerminal/LocalPixelScrollHeldRebase.swiftPackages/iOS/CmuxMobileTerminal/Sources/CmuxMobileTerminal/VerifiedReplayViewportAnchor.swiftPackages/iOS/CmuxMobileTerminal/Tests/CmuxMobileTerminalTests/LocalPixelScrollHeldRebaseTests.swiftPackages/iOS/CmuxMobileTerminal/Tests/CmuxMobileTerminalTests/VerifiedReplayViewportAnchorTests.swift
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At the local scrollback cap, rows pushed through the grid evict retained rows from the top while the row-space total stays flat. The verified-replay anchor restore cancels only total growth, so each restore preserves distance from bottom and the viewport drifts down over newer content (issue 9143 item 1). The same drift hits a mid-gesture held pixel-scroll position: eviction bumps row_space_revision, the held position fails the revision gate, and the batch rebases from a live viewport a replay just bottom-reset. Adds failing tests for pushed-rows-aware targetTopRow and for the pure LocalPixelScrollState.rebasedHeldPositionPx rebase decision, plus the inert API they compile against (the anchor field, parameter, and stub still reproduce today's behavior, so CI is red on the new expectations and green on the existing ones). Issue: #9143 Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
…the cap The phone's local mirror caps scrollback, so once a long-lived workspace pegs the cap every pushed row evicts a retained row from the top while the row-space total stays flat. Two paths re-applied stale row offsets and dragged a scrolled-up viewport down over newer content whenever output streamed: - The verified-replay anchor restore canceled only total growth, so at the cap it preserved distance-from-bottom; each replay restored the viewport scrolledRows lower in content space (both idle and right after a gesture). - Mid-gesture, eviction bumps row_space_revision, the held pixel position failed the revision gate, and the batch rebased from the live viewport that a full replay's alternate-screen roundtrip had just reset to the bottom. Fix: GhosttySurfaceView keeps a cumulative counter of rows its chunks push into local scrollback, incremented on the serial output queue as each screen-anchored delta's scroll prologue applies (frame.scrolledRows), so counter reads by anchor capture/restore and pixel batches on the same queue are exactly ordered against the pushes they account for. Anchor restores subtract max(growth, pushedSinceCapture) - pushes absorbed as growth keep top offsets stable, the remainder evicted retained rows. A revision-mismatched held gesture position is rebased the same way through the pure LocalPixelScrollState.rebasedHeldPositionPx decision instead of falling back to a bottom-reset live viewport. Rebuilt row spaces (hydration collapse) and rewound counters are detected and keep today's growth-canceled fallback, since local push accounting cannot place content in a rebuilt space. Closes item 1 of #9143. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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5dcc642 iOS: Keep Mac Awake is per computer — detail toggle, leading swipe action, row indicator (manaflow-ai#11092) 4c04923 fix(ios): content-true viewport anchoring while scrollback evicts at the cap (manaflow-ai#11185) 177d0df Fix iOS Tailscale pairing regression (manaflow-ai#11087) (manaflow-ai#11152)
…the cap (manaflow-ai#11185) * test(ios): content-true viewport anchoring at the scrollback cap (red) At the local scrollback cap, rows pushed through the grid evict retained rows from the top while the row-space total stays flat. The verified-replay anchor restore cancels only total growth, so each restore preserves distance from bottom and the viewport drifts down over newer content (issue 9143 item 1). The same drift hits a mid-gesture held pixel-scroll position: eviction bumps row_space_revision, the held position fails the revision gate, and the batch rebases from a live viewport a replay just bottom-reset. Adds failing tests for pushed-rows-aware targetTopRow and for the pure LocalPixelScrollState.rebasedHeldPositionPx rebase decision, plus the inert API they compile against (the anchor field, parameter, and stub still reproduce today's behavior, so CI is red on the new expectations and green on the existing ones). Issue: manaflow-ai#9143 Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> * fix(ios): content-true viewport anchoring while scrollback evicts at the cap The phone's local mirror caps scrollback, so once a long-lived workspace pegs the cap every pushed row evicts a retained row from the top while the row-space total stays flat. Two paths re-applied stale row offsets and dragged a scrolled-up viewport down over newer content whenever output streamed: - The verified-replay anchor restore canceled only total growth, so at the cap it preserved distance-from-bottom; each replay restored the viewport scrolledRows lower in content space (both idle and right after a gesture). - Mid-gesture, eviction bumps row_space_revision, the held pixel position failed the revision gate, and the batch rebased from the live viewport that a full replay's alternate-screen roundtrip had just reset to the bottom. Fix: GhosttySurfaceView keeps a cumulative counter of rows its chunks push into local scrollback, incremented on the serial output queue as each screen-anchored delta's scroll prologue applies (frame.scrolledRows), so counter reads by anchor capture/restore and pixel batches on the same queue are exactly ordered against the pushes they account for. Anchor restores subtract max(growth, pushedSinceCapture) - pushes absorbed as growth keep top offsets stable, the remainder evicted retained rows. A revision-mismatched held gesture position is rebased the same way through the pure LocalPixelScrollState.rebasedHeldPositionPx decision instead of falling back to a bottom-reset live viewport. Rebuilt row spaces (hydration collapse) and rewound counters are detected and keep today's growth-canceled fallback, since local push accounting cannot place content in a rebuilt space. Closes item 1 of manaflow-ai#9143. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> --------- Co-authored-by: Claude Fable 5 <noreply@anthropic.com>
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Fixes item 1 of #9143: with the local mirror's scrollback pegged at its cap, a scrolled-up viewport was pushed down over newer content as output streamed, both while idle and mid-gesture.
Every row a screen-anchored delta pushes through the grid either grows the local row space (below the cap) or evicts a retained row from the top (at the cap). Two paths only accounted for growth:
scrolledRowslower in content space. Observed in the issue as lines 4,354,666 → 4,362,346 at one offset over a 20s hold.row_space_revision, the held pixel-scroll position fails the revision gate, and the batch rebased from the live viewport that a full replay's alternate-screen roundtrip had just reset to the bottom.The fix keeps a per-surface cumulative counter of rows pushed into local scrollback, incremented on the serial output queue as each chunk's scroll prologue applies (
frame.scrolledRows), so counter reads by anchor capture/restore and pixel batches on the same queue are exactly ordered against the pushes they account for. Anchor restores now subtractmax(growth, pushedSinceCapture); a revision-mismatched held gesture position is rebased by the same arithmetic through the pureLocalPixelScrollState.rebasedHeldPositionPxdecision. Rebuilt row spaces (hydration collapse) and rewound counters are detected and keep the previous growth-canceled fallback, since local push accounting cannot place content in a rebuilt space; content-true anchoring across hydration still needs the producer-side counter tracked in the issue.This is a principled fix: it reconstructs the producer's monotonic scrolled-rows counter client-side (the approach the issue proposed) rather than patching a symptom. Residual risk: windows that span a hydrating full keep today's distance-from-bottom behavior.
Commit 1 adds the failing tests plus the inert API they compile against (stubs preserve old behavior so the new expectations are red); commit 2 adds the fix. The hosted
iOS simulator testslane cannot prove this right now: it is red on current main before any test runs (cmuxFeatureTests/MobileIrohRuntimeComposition*Testsno longer conform to the current broker protocols, andpackage-conventions-linthas 43 pre-existing violations). Red/green was instead proven on a leased fleet Mac (cmux-app-review-mac, iPhone 17 / iOS 26.3 simulator,xcodebuild testscoped to the CmuxMobileTerminal package): commit 1 (2107bda) fails with 7 issues, all of them the new content-true expectations; commit 2 (6fca0a3) passes the fullTest run with 21 tests in 2 suites. This branch adds zero lint violations (43 before and after; the new lock and helper are annotated/scoped per convention).Builds of this branch also need #11187 (main's macOS compile is broken by an unrelated bonsplit pin revert); the tagged dogfood build uses a throwaway
ctru-buildbranch = this head + that pin bump.HIG: scroll views must keep content stable under the user's finger and not move it unexpectedly while new content arrives (https://developer.apple.com/design/human-interface-guidelines/scroll-views).
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